The long range objective of this project is to identify gene products that determine the specialized morphology of a cell and to learn how they become localized in the cell. The cell studied is the amoeboid spermatozoon of the nematode C. elegans. The experimental approach is primarily genetic: isolation of morphological mutants and analysis of these mutants at the genetic, molecular and cellular levels. The specific aims are as follows: (1) To obtain mutations in the majority of spermspecific genes; more than 30 genes have been identified so far. (2) To continue ordering these genes into a pathway of development by light and electron microscopic examination of their mutant phenotypes, and by selection of suppressors and analysis of double mutations. (3) To continue cloning spermspecific genes taking advantage of the growing physical map of overlapping cosmid clones which now includes 66% of the genome. Cloned genes will be identified by hybridization to spermspecific RNA on Northern blots, and by microinjection of cloned DNA into mutant worms to assay for complementation of the mutation. (4) To identify mutant that alter the cellular localization of proteins in spermatocytes and spermatozoa using antibodies to individual gene products. (5) To sequence the cloned genes from mutants that alter cellular localization to learn about the structure of their protein products and identify targeting peptides and intramembranous domains; if some are homologous to other sequenced genes in the data bases, this may suggest their function. (6) If possible, to develop a reliable assay for in vitro assembly of the major sperm protein into 2-3nm filaments; to use this assay for analysis of mutants defective in assembly. This work is of general significance because the mechanisms by which genes specify the localization of cell components are fundamental to the differentiation of metazoan cells. Understanding these mechanisms may give insight into the genetic basis for the heritable changes in cell shape that invariably accompany malignant transformation as well as the genetic defects leading to developmental diseases and birth defects.